To enable an acceptable representation of high-dynamic range (HDR) imagery on a display with a dynamic range that is typically several orders of magnitude lower, the dynamic range of recorded video sequences is usually compressed by means of tone-mapping during acquisition and transmission. The dynamic range of many outdoor scenes can be as large as 12 orders of magnitude, whereas most liquid crystal displays (LCDs) merely offer a static contrast ratio of about 3 orders of magnitude. As a result severe dynamic range compression is required in the early stages of the imaging pipeline to enable a pleasant representation of the scene on a LDR (low dynamic range) display. Using simple techniques usually has the drawback that the contrast of small details can be compromised or even lost.
To address these shortcomings, more advanced adaptive methods have been developed. These methods predominantly compress large-scale contrasts while preserving the contrast of fine details.
This approach performs well as long as the display system's capabilities remain more or less similar to those anticipated during compression in the early stages of the imaging pipeline. However, with new high-dynamic-range display systems, static contrast ratios of up to 6 orders of magnitude can be achieved. Moreover, such display systems may be capable of locally (in time or space) producing a very high peak brightness. For example, this can be achieved by 2D dimmable LED backlights, where the power saved by dimming some LEDs underneath dark image portions may be used to boost other LEDs underneath bright regions. An extension of the input LDR image data into a HDR image signal has been found to often result in an unnatural appearance of the scene.